Merge branch 'tc-revert-rails5-workaround' into 'master'

Revert "Workaround for Rails 5, where LIMIT..."

See merge request gitlab-org/gitlab-ce!30780

lib/gitlab/database/subquery.rb

@@ -6,11 +6,7 @@ module Gitlab
       class << self
         def self_join(relation)
           t = relation.arel_table
-          # Work around a bug in Rails 5, where LIMIT causes trouble
-          # See https://gitlab.com/gitlab-org/gitlab-ce/issues/51729
-          r = relation.limit(nil).arel
-          r.take(relation.limit_value) if relation.limit_value
-          t2 = r.as('t2')
+          t2 = relation.arel.as('t2')
 
           relation.unscoped.joins(t.join(t2).on(t[:id].eq(t2[:id])).join_sources.first)
         end